Why Napoleon spared Gottingen

The French army was approaching Gottingen,in Germany during 1807 war.Then, Napoleon ordered his troops to spare the city ,and instructed to move to next city without any disturbance in Gottingen. The troops got surprised. Then Napoleon explained: "A great mathematician is living in Gottingen, and we should not disturb him,as the world needs his knowledge and service. Carl Fredrich Gauss was that Mathematician ! and 23rd Feb is his remberance day